Failed to send Prolog

Hi all, I am a newbie of Linux and OCS inventory. I have installed OCS server in my CentOS 8 and I can login to the admin portal but my PC information cannot send to my CentOS 8 OCS server.

can anyone help me? Thank you very much.
Here is my PC ocsinventory.ini;

[OCS Inventory Agent]

ComProvider=ComHTTP.dll

Debug=1

Local=

NoSoftware=0

HKCU=0

NoTAG=0

IpDisc=

[HTTP]

Server=http://10.106.64.63/ocsreports

SSL=0

CaBundle=cacert.pem

AuthRequired=0

User=

Pwd=

ProxyType=1

Proxy=mycompanyproxyserver

ProxyPort=8080

ProxyAuthRequired=0

ProxyUser=

ProxyPwd=

[OCS Inventory Service]

TTO_WAIT=22860

INVENTORY_ON_STARTUP=0

Here is my PC Agent log;

Starting OCS Inventory Agent on Monday, December 14, 2020 15:04:48.

AGENT => Running OCS Inventory Agent Version 2.8.0.0

AGENT => Using OCS Inventory FrameWork Version 2.8.0.0

AGENT => Loading plug-in(s)

DLL PLUGIN => Searching for Plug-in DLL(s) in folder <C:\Program Files\OCS Inventory Agent\plugins>

DLL PLUGIN => 0 DLL Plug-in(s) successfully loaded on 0 DLL(s) found

AGENT => Using network connection with Communication Server

COM PROVIDER => Loading Communication Provider <C:\Program Files\OCS Inventory Agent\ComHTTP.dll>

AGENT => Using Communication Provider <OCS Inventory cURL Communication Provider> Version <2.8.0.0>

AGENT => Sending Prolog

DID_CHECK => Read DeviceID <NHK-NB-N3159-05-2020-11-09-10-11-06> and MACs <00:05:9A:3C:7A:0000:50:56:C0:00:0144:85:00:3B:45:B050:7B:9D:CE:2D:1200:50:56:C0:00:08> in file <ocsinventory.dat>

COM SERVER => Initializing cURL library for sendRequest

COM SERVER => Using cURL without server authentication

COM SERVER => Using cURL HTTP type proxy <mycompanyproxyserver:8080>

COM SERVER => Using cURL proxy without authentication

COM SERVER => Disabling cURL SSL server validation support

COM SERVER => Sending HTTP Post request to URL <http://10.106.64.63/ocsreports>

COM SERVER => HTTP Post response received <HTTP Status Code #503>

COM SERVER => Cleaning cURL library

ERROR *** AGENT => Failed to send Prolog <HTTP Status Code #503>

AGENT => Unloading communication provider

AGENT => Unloading plug-in(s)

AGENT => Execution duration: 00:01:26.